This invention relates to devices for the fixation of fractured bones and in particular to a device for the fixation of fractures involving long bones, such as subtrochanteric and intertrochanteric fractures of the femur.
The successful fixation of any fractured long bone is generally dependent upon two basic considerations. First, the fracture site should be rigidly maintained in compression to stimulate bone repair; and second, shear, rotational and angular stresses at the fracture site should be minimized (and if possible eliminated) as such stresses inhibit bone union. In fractures involving the proximal aspect of the femur, for example, these considerations are particularly important due to the considerable magnitude and complex distribution of the forces to which this region is subjected. (Loads up to four times body weight may be transmitted through this region during the gait cycle.)
Heretofore, the fixation of fractures of the proximal femur has typically been attempted by the insertion of a hip compression screw, usually comprising a lag screw to be secured in the femoral head, a compression plate cooperable with the lag screw to be secured to the femoral shaft and a compression screw for attaching the compression plate to the lag screw and applying a compressive force therebetween. Such devices have also been more generally used for the fixation of fractures in which one major fragment is mostly cancellous and the other fragment is primarily cortical (e.g., supracondylar fractures of the distal femur).
Although prior hip compression devices are effective for the fixation of certain types of fracture configurations involving the proximal femur (more specifically, certain intertrochanteric fracture configurations), there are many fracture configurations for which these devices perform poorly or are ineffective. For example, in the case of subtrochanteric fractures of the proximal femur (as well fractures in other regions such as supracondular fractures of the distal femur), prior hip compression devices can allow significant shear, rotational and angular forces to occur while failing to provide the desired compressive forces at the fracture site. In practice, such characteristics may lead to a loss of reduction, nonunion or malunion of the fractured bone and even breakage of the device subsequent to insertion.
The present invention overcomes these deficiencies and other disadvantages of the prior art.